N3Fusion Energy Development Strategy and the ITER Program
核融合エネルギーの開発戦略と ITER 計画
Mitsuru Kikuchi
菊池 満Japan Atomic Energy Research Institute, Naka Fusion Research Establishment
801-1, Mukoyama, Naka-machi, Naka-gun, Ibaraki, 311-0193, Japan
日本原子力研究所那珂研究所、〒311-0193 茨城県那珂郡那珂町向山 801-1
Fusion energy is one of possible options of future energy sources for humankind. The fusion energy
has intrinsic advantages over other future energy options. And it is scientifically challenging since it
requires to confine and to sustain high temperature plasma of a few 100 million degree far exceeding thetemperature of the center of the Sun. The ITER is right now a most important step towards the fusionenergy development in which control of burning plasma is addressed. Flexible and well-thought strategy
for fusion energy development is required for early contribution to the energy market and stabilization of
atmospheric CO2 concentration.

1. Introduction
The Sun is a mother of all living on the Earth.
Source of the energy of the Sun is fusion reaction as
discovered by Hans Bethe in 1939. Fusion research wasstarted at around 1950 as an exciting challenge of thehuman kind to realize a Sun on the Earth. Confinementof high temperature plasma is needed to realize a Sunon the Earth. The plasma is a fourth state of matter andwas not familiar for physicists and engineers although
99% of the universe was made of plasma. It took about
45 years for fusion researchers to realize equivalent
break-even (break-even: ratio of fusion power to net
input power is 1) plasma with a strong support by thepeople and the people’s government. Human being now
knows how to produce high temperature plasma up to520 million degree in large tokamaks such as JT-60 [1].
Scientific knowledge during 55 years of fusion
research enabled us to design and construct a fusion
experimental reactor, the ITER. We have good
confidence to achieve technical objectives of ITER [2].
Fusion research is a long-term scientific activities neverexperienced by the Human being. It requires strong will
to fulfill long-term scientific program for realizing a
Sun on the Earth. Fusion DEMO next to ITER will be alast step before the commercialization of fusion energy
following so-called “Fast Track” approach to Fusion
Energy [3]. This two-step approach to fusion energy
becomes possible with a strong accompanying program
such as continued concept improvement of tokamak
configuration and also fusion technology development.
This year (2005) is named as “Einstein Year” sincehundred years has passed since his discovery of E=mc2
relation in 1905. And this year it is timely to discuss
fusion research in which energy is produced through his
famous relation.

2. The ITER
The programmatic objective of ITER is todemonstrate scientific and technical feasibility of fusionenergy. It is important to understand that feasibility offusion energy depends on the outcome of ITER. If
ITER is successful enough, technical feasibility offusion energy becomes firm as documented by thereport of the Subcommittee of the Fusion Council forFusion Development Strategy [3].
The technical objectives of ITER is set todemonstrate key elements of the control of selfsustained fusion burn, namely to sustain Q≧10 for 400
seconds without precluding Q=∞, to aim at Q≧5 noninductive steady-state operation, integral demonstrationof number of essential reactor technologies, component
test for a future reactor such as divertor heat and power
control, and test of tritium breeding module concepts
[2].

6.2m

Fig. 1 Bird’s eye view of the ITER

Impact of ITER technical objectives on thedevelopment path towards fusion energy was discussed
in ITER SWG report #2 [4]. The ITER represents ademonstration of fusion technologies under powerplant-relevant conditions: super-conducting magnets,
additional heating, fuel handling and vacuum pumping
systems, plasma facing components. The ITER also
provides the opportunity to explore the compatibility of
improved tokamak modes and profile control in regimesof strong self-heating and steady-state operation as atest for tokamak power plant operation.
In order to proceed to a demonstration power plant(DEMO), ITER should address many physics andphysics-technology issues such as,- steady-state burning plasma with current driven
profile control and a high bootstrap current
fraction.
- A high performance core with an effective
divertor, including high heat-flux steady-statecomponents- Test of tritium-producing blankets and ofstructural materials
Steady-state operation with Q ≧ 5 will be an
important Japanese milestone for ITER. It is also quite
important to develop “soft” divertor plasma with which
divertor plates could withstand high heat and particle
fluxes for year-long operation in DEMO. Moreover,higher beta operation is needed for the DEMO reactor
since it becomes a prototype of company-led 1st
generation commercial reactor. For such test operations
in ITER, further proof of non-inductive steady-state
operation and also exploration of high beta operation isrequired in accompanying program before the test inITER.
3. Program in parallel with ITER
Since ITER is an international program, any testprogram in ITER requires agreement amongparticipating parties. So unproven experiments under
non-DT facilities have a difficulty for adoption,
especially in case that it needs some investment. In thisrespect, domestic program giving a confidence for sucha test in ITER plays an important role in leading andmaximizing productivity of ITER research.
If such a domestic program has unique feature that
could not be realized in ITER, it will contribute toexpand a possible design window of DEMO, notlimited to ITER configuration. The working group forfusion research under council for science andtechnologies identified such a feature as high beta
steady-state operation with shape, aspect ratio, andfeedback control enhancement that significantlycontributes to the economical viability of fusion energythat was originally planned to be demonstrate inPrototype fusion reactor after DEMO before theappearance of “Fast Track” approach [3].
It is also quite important to develop fusion reactor
materials through irradiation tests of likely candidate
materials such as reduced activation ferritic steel by
14MeV neutron source such as IFMIF to validate
applicability of such materials and also obtain
irradiation data for design and improvements ofcomponents as endorsed by the working group on
fusion research [5]. Efforts should also be made on
development of high temperature blanket system that isessential for the DEMO reactor.
Also development of safer and environmentallyacceptable (with respect to waste management) reactor
concept is important for better public acceptance.
4. Discussion
Above-mentioned research items are quite
essential for a decision of construction of DEMO.
DEMO could be constructed if the extrapolated COE(cost of electricity) to 1st commercial reactor meets theuser requirement, and if the extrapolated safety features
to 1st commercial reactor meet the public needs, and if
the extrapolated operational reliability meets the userrequirement, etc. Assessment of breakeven price wasmade by K. Tokimatsu that gives good long-term target
for fusion economy[6]. Also, recent analysis by K.
Tobita showed that significant reduction of fusion radwaste is possible with proper selection of radial build
and materials [7]. Fusion development strategy should
be well-thought and be flexible to allow adoption ofimprovements in various fields into a core program. It isquite important to balance various issues according to aprogress of research accomplishments for early
realization of fusion energy.
References[1] M. Kikuchi, N. Inoue, "Role of Fusion Energy forthe 21 Century Energy Market and Development
Strategywith
International
Thermonuclear
Experimental Reactor ", 18th World Energy Congress,
Buenos Aires, 2001. DS6 Paper number 01-06-09[2] ITER Special Working Group, ITER SWG report tothe ITER Council on Task #1. May 1998.
[3] The Subcommittee of the Fusion Council for Fusion
Development Strategy, Report on Technical Feasibilityof Fusion Energy and Extension of the Fusion Programand Basic Supporting Researches.
[4] ITER Special Working Group, ITER SWG report tothe ITER Council on Task #2. Jan. 1999.
[5] Working group on fusion research, council forscience and technologies, “Future Direction of National
Fusion Research”, Jan. 8, 2003.
[6] K. Tokimatsu et al., Nuclear Fusion 42(2002)1289.
[7] K. Tobita et al., J. Nuclear Materials 329333(2004)1610.